Issue 31

C.L. dos Santos et alii, Frattura ed Integrità Strutturale, 31 (2015) 23-37; DOI: 10.3221/IGF-ESIS.31.03 32 placed in the side member along the horizontal LT plane containing the hole axis (see Fig. 8). This interface was placed in the most likely position for the initiation and propagation of cracks in the side members. Besides the simulation of the T-connection using standalone constitutive modelling approaches - plasticity and cohesive damage modelling, two mixed constitutive modelling approaches were also investigated for the joint, as documented in Tab. 6. Firstly, the centre member was considered with elastic-plastic behaviour, through the implementation of the Hill's plasticity model and the lateral member was considered elastic and showing a cohesive interface (Elastic-plastic with cohesive (1)). This approach takes into account the higher embedding strength, experimentally verified in the centre member. Finally, all wood members were assumed elastic-plastic and the cohesive interface on the side member was preserved (Elastic-plastic with cohesive (2)). In both approaches, the Hill´s plasticity model was applied, using the constants of the Tab. 3. The cohesive damage model parameters from Tab. 5 were maintained. Figure 8 : Cohesive interface representation. Results and discussion In this section, the results of numerical simulations, using the constitutive modelling approaches summarized in Tab. 6, will be presented and compared with the experimental results, particularly the load-displacement curves obtained for the T-joint. Fig. 9 compares the numerical responses from the simulations with plasticity models. The load-displacement curves shown in Fig. 9 under the “elastic-plastic (1)” series were obtained using the same plasticity constants for both wood members. The consideration of distinct plasticity constants, for each wood member, resulted in an improved load- displacement curve, as demonstrated by the “elastic-plastic (2)” series (see Fig. 9). Figure 9 : Load-displacement curves: experimental vs. elastic-plastic analysis results. The experimental curves exhibit a non-linearity at the beginning of tests, which is due to some initial embedding between the steel dowel and wood, motivated from wood surface damage due to the drilling/cutting process, surface imperfections and small misalignments. The numerical models do not describe this behaviour; therefore numerical curves were subjected to a horizontal shift of 0.5 mm. In general, the numeric curves reproduced satisfactorily the initial part of the test results